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342                          DISAPPEARANCE OF HAIR                          CHAP.
by a few hairs only—so few that they can be counted with ease
—in the neighbourhood of the muzzle. These hairs are not
present in all Whales; they are absent, for example, in the White
Whale or Beluga. When present they are not furnished either with
sebaceous glands or with muscular fibres, "which are such universal
concomitants of the hair follicles in the Mammalia generally.
This appears to be conclusive evidence that the hairs, few as they
are, are still undergoing degeneration. The need for a furry
coat is removed by the presence of a thick coating of fat im-
mediately underlying the skin. This is known as the blubber,
and is the main incentive to the pursuit of W hales. It miist
not, however, be assumed without further argument that the hair
is absent because its place is taken, as a mechanism for retaining the
heat, by the blubber; for the Seal tribe possess both fur and blubber.
Another conceivable explanation is quite at variance with such a
view of economy. It may be noticed that among Ungulates there
is a tendency to lose hair, particularly among more or less aquatic
forms. Thus the Hippopotamus is almost naked (as is indeed the
Walrus) ; the Rhinoceros, too, often a frequenter of marshy soil, is
almost as denuded as is the Hippopotamus. It is not, however,
settled that the Whales have anything to do with the Ungulata ;
otherwise an additional argument might be used, that is, the
secular loss of hair in some members of this group. The Hairy
[Rhinoceros, Kh,« ticfaorhinus, was, as its name denotes, a hairy
beast; the Mammoth was equally so. The descendants, or at
least the modern representatives of both these creatures, are but
scantily clad with hairs.
A final reason for the naked character o£ the skin in exist-
ing Cetacea is closely connected with a feature in uhe organisa-
tion of three or four living species which must first be
described.
Some years ago the late Dr. J. E. Gray of the British Museum
described from the sea, off Margate, what he considered to be a
new species of Porpoise, characterised by the presence on the
dorsal fin of a row of stony tubercles. As a matter of fact it
was subsequently shown that the Common Porpoise has the same
sfcroetures, so that there was no need for a Margate species,
t<wbvrmd$/&ra. Moreover, in the Indian Jieomerisf a
aHy of the Porpoise, a more abundant calcified covering of
along the whole back of the animal. These plates,